U.S. security agents are doing it on the sly, reports CBS News correspondent Bob Orr: They're separating legitimate air travelers from would-be terrorists.
While X-ray machines and explosive scanners focus on weapons, Transportation Security chief Kip Hawley said Tuesday that screeners are studying passengers for signs of nervousness.
"It is involuntary muscular behaviors that are across the board, that doesn't matter what you look like. You don't have to look like a terrorist to exhibit these involuntary behaviors," he says.
It's the first step in so-called behavioral profiling. The next step can be seen inside a lab at the University of Buffalo, where a research suspect is about to tell a lie.
"I'm officer Ray LaHocking and I'd like to ask you a few questions … "
"OK," nods the suspect. "There's gonna be a person I talk to and I'll sign some forms."
So where's the lie?
"When he says 'there's a person I'm gonna talk to and I'm gonna go sign some forms,' you actually see a sign of fear/anxiety that hits him at that particular moment," says psychologist Mark Frank.
What Frank saw was a split-second tightening of the muscle in the center of the forehead.
"It's across the top of the eyes, in the eyebrows," he says. "It's part of a facial expression of fear."
The flash of fear is called a "micro-expression." It's an involuntary facial response that can betray a liar.
"When people have emotions, the same areas of the brain that are responsible for causing the heart rate to go up and your blood pressure to go up and the little sweat you get on your hands are also sending a pulse to your face," Frank says.
Frank, who's developing the profiling technique for the Department of Homeland Security, claims he can spot a liar 90 percent of the time.
"I think at this point it is at least as accurate as a polygraph," he says.
Frank says the kind of behavioral analysis he's doing in his lab can be taught to screeners in the real world with as little as 30 minutes training. Hundreds of faces have convinced him the science is solid in identifying people who might be lying.
"If it just helps you make one or two better judgments," Frank says, "that could be the difference."
Frank concedes facial profiling is not foolproof — there is no absolute way to spot a lie. At the same time, terrorists should take no comfort — there's also no such thing as a fail-safe poker face.